The present invention relates to an improved hydrophilic colloid composition based on konjac that readily hydrates and forms a highly viscous and stable gel and is therefore useful in a wide range of useful products including food, cosmetic, medicinal and dietary supplement compositions and others, particularly those requiring properties of rapid, simple hydration with stable viscosity maintenance over wide ranges of temperature and concentration.
The use of hydrocolloids, such as konjac, for improving the viscosity and flow of aqueous liquids has been known for years. Konjac and some other hydrocolloids absorb and retain large quantities of water relative to their dry weights and form viscous gels. Due to its exceptional water retention capability, konjac is used in a variety of applications. Many improvements have been made to utilize konjac and other naturally-derived materials with improved purity and functionality. Konjac falls into the general category of compositions referred to as hydrophilic colloids, which are compositions capable of mixing with water or other aqueous liquid to form a hydrocolloid, which can be a thickened or gelled material. Hydrophilic colloids can be naturally derived, like konjac, or obtained synthetically. In the case of natural hydrophilic colloids, they can be derived from animal or vegetable sources, with konjac being from vegetable sources. In general, hydrophilic colloid molecules have an affinity for water molecules and, when dispersed in water, become hydrated. Hydrated colloids (hydrocolloids) swell and increase the viscosity of the system, thereby improving stability by reducing the interaction between particles and their tendency to settle. Hydrophilic colloids are generally taken to include colloid systems wherein the colloid particles are dispersed in water (a colloid system is simply a mixture in which two substances are interspersed between each other). Konjac and other hydrophilic colloids are known to be used in combination in various stages of purification.
The colloid particles in a hydrocolloid may possess a net surface electrical charge, the sign of which can depend on the chemical properties of the colloid and the pH of the system. The presence of a surface charge produces repulsion of the charged particles and thus reduces the likelihood that the particles will adhere to one another and settle. Hydrocolloids, thus, are typically in the form of charged colloid particles distributed throughout water or other aqueous phase. Depending on the amount of available water, such a hydrocolloid can take on different states, typically being in the form of a gel or sol (liquid). Hydrocolloids can be either irreversible (single state) or reversible, e.g., they can exist in a gel and sol state and alternate between states by heating or cooling. Because their stability can depend on pH, charge, concentration, and temperature, there are a number of factors that can be helpful or the opposite to stability.
To best achieve the degree of stability required for a particular use, the natural sources of hydrophilic colloids are purified and particulated in dry form. The dry hydrophilic colloid materials, like konjac, however, are often very difficult to dissolve in cold water and often even in warm water. When purified, however, materials like konjac often take up water so quickly at their surfaces that clumps form without achieving a thorough hydration necessary to form a stable hydrocolloid. The clumps take excessive periods of time to hydrate or in some situations fully fail to hydrate for practical application.
There is a need for konjac based gelling agents that can rapidly hydrate, e.g., fully dissolve in water to reach peak viscosity in 2 minutes or less at 70° C., and at room temperature (e.g., 25° C.) reach about 50% of peak viscosity in 10 minutes, and peak viscosity in less than an hour. The fast hydration is attributable to the combination of finer konjac particles and the presence of the supporting agents.
Regular konjac, as commercially available, forms excessive amounts of lumps when mixed with water, even under agitation. There is need for improvement to avoid or ameliorate the natural interactions between konjac and water and other useful compositional components. While konjac is highly desired for its ability to form hydrated gels, the gels formed from commercial konjac lack the stability that would be desired for the economical and efficient use of the compositions in their gel forms. Regular konjac gel loses a significant amount of its viscosity after 5 to 10 hours at room temperature. It would be desirable to provide konjac compositions that could maintain up to 90% or more of peak viscosity for several days, e.g., as long as 4-5 days, at room temperature. Improvement in stability at elevated and reduced temperatures, e.g., −10° C. or 120° C., would also be desirable and cannot be satisfactorily achieved with current commercial compositions while also having good dispersibility under practical conditions.
There are a lot of impurities in the regular konjac powder, and we have found that even purified forms contain impurities that impart a distinctive smell, which is acceptable for some situations but limits the uses of konjac, especially in food applications. Moreover, the impurities limit solubility and can cause undesirable interactions, limiting uses for point-of-service settings. Konjac and some other hydrocolloids absorb and retain large quantities of water relative to their dry weights and form viscous gels. Due to its exceptional water retention capability, konjac is used in a variety of applications. Other purity considerations are important for products used in the petroleum drilling fluid where fast hydration and high viscosity are very important, and in detergents, paper, textiles, creams/lotions, adhesives, and so on, where color, odor and shelf-stability are important.
Regular konjac, as commercially available, is difficult to use. Preparing konjac gels and solutions is difficult and time consuming. It often takes 2 to 6 hours to dissolve regular konjac powder in water. Even at relatively high temperatures of 80° C. or higher, rigorous agitation is required to ensure full dissolution, resulting in high energy costs. Without agitation, konjac forms un-dissolved lumps that decrease the quality of the final products. Given the high viscosity of konjac gel even at a low concentration, rigorous agitation consumes a significant amount of energy and may not even be practical for certain applications.
Efforts have been undertaken to improve dissolvability of konjac. One strategy is to use finer konjac powder. However, simply grinding regular konjac generates large amount of heat which may disrupt molecular structure of konjac. Conventional grinding not only causes the konjac flour to degrade as evidenced by its turning brown and smelling burnt, but also causes a large reduction in attainable viscosity.
It was reported in U.S. Pat. No. 5,733,593 that fine konjac powder could be produced by grinding deep-frozen konjac powder. The fine powder dissolves more rapidly than regular konjac. However, this procedure is capital intensive and has high production cost. In addition, the fine powder alone does not solve the lump formation issue completely and purity issues remain. Moreover, konjac gel, from either regular or fine powder, loses significant viscosity after 5 to 10 hours at room temperature. This instability reduces the applications of konjac.
Other hydrocolloids have been shown to have synergistic effects when combined with konjac. Among these, xanthan and carrageenan have been shown to improve the strength and viscosity of the konjac gel. This is presumably due to non-covalent interactions among different polysaccharide chains. However, simply combining these other hydrocolloids with konjac does not improve the speed of dissolution. It still takes hours for full hydration of the simple combination hydrocolloids. High temperatures (80° C. or higher) and constant agitation are still required to fully dissolve the konjac power. Neither does this simple combination solve the lump formation issue of konjac. In U.S. Pat. No. 5,462,761, there is described an aggregate composition comprising microcrystalline cellulose and glucomannan, which is derived from konjac. The konjac glucomannan, the inventors say can be native (crude) konjac flour, clarified konjac glucomannan, cold-melt konjac or preferably purified konjac glucomannan, all of which are known in the art. Their composition comprises aggregate particles of microcrystalline cellulose (MCC) covered with glucomannan. The average particle size of the inventive dry MCC/glucomannan spheroidal particles is 0.1 to 100 microns, e.g., most preferably 12 to 35 microns. These compositions are said to be particularly useful as bulking agents and as fat replacers, especially in water-based formulations used as foods. Testing, which entailed mixing with water in a blender at 15,000 RPM for 15 minutes, summarized in Table 1, emphasized the texture of hydrated composition as being “smooth, spheroidal particles” as opposed to a gel. It would be desirable to utilize the gel-forming capabilities of konjac in a composition which enabled rapid, easy hydration.
In U.S. Pat. No. 5,536,521 to Shelso, et al., there is described a rapidly hydratable konjac flour which is said to gain at least 60% of its potential peak viscosity within 10 minutes after dispersal into water at 25° C., at least 80% of its potential peak viscosity within 20 minutes after dispersal into water at 25° C. and from 80 to 100% of its potential peak viscosity within 30 minutes after dispersal into water at 25° C. Among the methods disclosed are two-step flaking and grinding; however, despite the rigorous processing, improved purity and functionality would still be desired.
In another patent mentioning konjac and microcrystalline cellulose, U.S. Pat. No. 5,605,712, describes a stabilizer composition, said to be useful for stabilizing frozen desserts, having (a) a first component of microcrystalline cellulose (MCC) coprocessed with a calcium/sodium alginate salt complex and containing sufficient MCC such that the weight ratio of MCC to alginate salt complex is greater than about 80:20, in combination with (b) a second component of at least one water soluble hydrocolloid selected from the group consisting of guar gum, locust bean gum, sodium alginate, carrageenan, gum tragacanth, karaya gum, gum arabic, agar, konjac, xanthan gum, carboxymethylcellulose, methylcellulose, hydroxymethylcellulose and hydroxypropylmethylcellulose. The teachings leave the person skilled in the art with the need for improvements in the gelling, stability, hydration and purity of the konjac.
In U.S. Pat. No. 5,624,612, there is described nonaggregating hydrocolloid microparticulates, which are said to be substantially dry, rehydratable, water-dispersible, gel-forming, and porous. They are described as containing a gelling hydrocolloid like konjac and internally or internally and externally at least one water-soluble, non-gelling, hydration enhancing hydrocolloid, such as various gums, and can include water-soluble components like konjac. Again, the thrust appears to be to prepare having particular utility as fat replacement components in foods, without providing other needed improvements in ease of hydration, solubility, purity and stability.
Konjac has been proposed for use in a wide variety of foods. For example, in U.S. Pat. No. 4,582,714, there are described ungelled processed food products, particularly emulsions, containing a stabilizing or thickening agent, such as ice cream, whipping cream, cheese spreads, cheese slices, milk drinks, meringues and the like. These products, which when produced on a commercial scale normally incorporate a stabilizing and/or thickening agent to improve their processability, texture, organoleptic properties and storage capability. There, conventional stabilizing and thickening agents, such as carob gum and/or cellulose ethers such as the hydroxyethyl and carboxymethyl ethers, are replaced with glucomannans, especially those derived from Amorphophallus species and especially from A. rivieri and its varieties (often referred to as A. konjac). In U.S. Pat. No. 6,548,097, konjac is said to be useful in preparing frozen confections comprising a gel composition. And, in U.S. Pat. No. 5,665,418, there is described a fibrous and granular konjac prepared from solidified konjac said to be suitable for processed foods or as a dietary food by itself. It is prepared by crushing a kneaded and solidified mixture of konjac roots and lime to form granular and fibrous pieces that are about less than 6 mm long and contain 5 to 10% moisture. Again, improvements are needed in ease of hydration, solubility, purity and stability.
Among the various uses of konjac is as a textural components for beverages and other liquids. In U.S. Pat. No. 6,730,336, there are described fortified beverages with improved texture and flavor impact at lower dosage of solids. Konjac and other carbohydrates are suggested as fat mimetic materials in beverages. To similar effect are U.S. Pat. No. 6,379,737, which describes a dissolution agent for making rapidly soluble instant beverage products, and U.S. Pat. No. 6,290,997, wherein the texture and flavor impact of beverages is modified at low dosage of solids. In U.S. Pat. No. 6,673,384, konjac mannan is one of a number of materials suggested to add a creamy mouth feel agent for foods and beverages. And, in U.S. Pat. No. 6,042,854, gellan gum is used to improve physical stability of liquid nutritional products normally stabilized with konjac or other stabilizers. In U.S. Pat. No. 6,582,749, konjac can be added to low fat edible emulsions. U.S. Pat. No. 6,455,090, relates to a liquid additive thickener which can contain konjac as a thickener to help form viscous solutions and gels to thicken gravy, dressing, sauce, mousse and jelly. In U.S. Pat. No. 5,700,513, liquid nutritional product containing improved stabilizer composition in gelatinous food products particularly suitable for nutrition of patients with dysphagia and has good eating qualities, for instance, ease of swallowing, owing to the soft jelly form. Xanthan gum, konjac mannan, or the like, may be used as a part of a gelling agent. And, in U.S. Pat. No. 7,037,539, there is disclosed a strawberry fruit juice drink made with konjac or other hydrocolloid gum as a thickener. In each of these cases, there remains a need for improved ease of hydration, solubility, purity and stability.
There are yet a wide variety of known uses for related gums, including well treatment fluid compositions as described in U.S. Pat. No. 6,983,801, wherein a well treatment fluid composition comprises a solvent (such as water), a polymer soluble or hydratable in the solvent, a crosslinking agent, an inorganic breaking agent, and an ester compound. Preferably, the hydratable polymer is a polysaccharide, such as galactomannan, cellulose, or derivatives thereof. In U.S. Pat. No. 6,685,978, there are described gelled and gellable compositions for food products. The principal description is of gel-in-place compositions for food products, as well as to food products including the gel-in-place compositions. The preparation, storage, distribution and cooking of food products is said to be improved without excessive seepage of liquid from the food products. The patent describes the use of various polysaccharides, including konjac gum that can form a thixotropic gel. In U.S. Pat. No. 6,558,652, there is described a process for producing glucomannan gel particles wherein a particulate glucomannan gel is produced by swelling a glucomannan-rich flour with water in the presence of ethanol, treating the swollen particles with an alkali to form gelled particles followed by drying. The dried gel particles are incorporated into hygienic or cosmetic preparations as a deposit-cleaning agent. U.S. Pat. No. 6,531,169 describes a composite food composition, in particular a frozen water ice confection in which two or more component phases are present in an intermingled manner that is neither consisting of distinct component blocks of phases, nor present as a fine mixture(s) of phases, and in which at least one of the component phases comprise a polyanionic gel. Konjac is described as an optional neutral hydrocolloid, which can be included. U.S. Pat. No. 5,789,004, describes a stabilizer composition, useful for reduced fat frozen desserts and whipped toppings, containing, as a first component, microcrystalline cellulose coprocessed with guar and, as a second component, microcrystalline cellulose coprocessed with carboxymethylcellulose. Konjac is identified as one of many useful hydrocolloids. In U.S. Pat. No. 4,894,250, there are described thermo-irreversible edible gels of glucomannan and xanthan gums, with konjac as an optional ingredient, useful to simulate the texture of natural meat offals. U.S. Pat. No. 4,844,913 describes a low-calorie foodstuff for processed food comprising gel-particles of glucomannan coagulum and also a low-calorie processed food comprising gel-particles of glucomannan coagulum. In particular, the description utilizes konjac glucomannan in the preparation of functional foods and provides a dietary fiber food component. And, in U.S. Pat. No. 4,676,976, there is described a konjak mannan-containing reversible gel useful in preparing processed meat products comprising a thermally treated, uniform mixture of a meat and a konjac mannan gel. The konjac mannan gel is obtained by steaming a sol of konjac mannan gel.
Thus, despite the wide use of konjac over a long period of time, there remains a need for improved ease of hydration, solubility, purity and stability.